Structural and dielectric properties of aluminum-doped GaFeO3

Ga0.9Al0.1FeO3 and Ga0.75Al0.25FeO3 samples were obtained using a solid-state reaction process. Phase analysis indicated that all samples are single phase having an orthorhombic structure. The effect of Al doping on the lattice parameters, the distortions in the tetrahedral and octahedral bond lengths and angles and cation distribution of different ions among the four crystallographic positions in GaFeO3 (GFO) was studied in detail applying Rietveld structural analysis; Al ions substituted Ga mostly at the octahedral site G2 with a small fraction residing at the Fe1 and Fe2 sites. The sample morphology was investigated by high-resolution scanning electron microscopy and the corresponding energy-dispersive x-ray analysis manifested element percentages in accordance with intended values. The influence of the doping amount, the frequency and temperature on the dielectric properties, ac conductivity, complex impedance and complex electric modulus of GFO was also investigated. Nyquist plots for both samples at different temperatures were studied. The activation energy of doped samples is in agreement with the activation energies of double ionized oxygen vacancies; it increased as the amount of Al doping GFO matrix increased.